A clinical biomarker assay to quantitate CXCL9 in human serum

To assess circulating CXCL9 as an exploratory biomarker in clinical studies, an electrochemiluminescence CXCL9 assay was validated in human serum to define assay conditions that can remove matrix effect, improve precision and accuracy, as well as establish sensitivity and reportable range. The validated assay demonstrates ultra-sensitivity with a lower limit of quantification of 1.64 pg/mL in human serum. This assay exhibits optimal precision and accuracy. In addition, biological variability and CXCL9 stability in human serum were also assessed. The validated assay is an exploratory clinical biomarker assay that enables assessment of CXCL9 as an exploratory pharmacodynamic or predictive marker that correlates with clinical response in clinical studies.